In offshore operations, as for example offshore well drilling and producing of petroleum products from a fixed structure, a considerable quantity of water is normally withdrawn from the earth during the producing operation. The water is generally intermixed with, or in suspension with crude oil, gas, or other liquids even though not forming a solution therewith.
Thus, during the initial processing of the produced product such as crude oil, it is necessary to dispose of the water. The most practical outlet for such disposal would be merely to discharge it overboard from the offshore structure. Normally however, the water is treated prior to such discharge to remove as much as possible of the matter contained therein which would tend to pollute the surrounding environment.
In accordance with the instant invention, means is provided to avoid any possible environmental degradation resulting from the discharge of materials into the surrounding body of water. This is achieved by depositing the polluted water in its entirety into a pile or caisson which is so constructed to contain the discharged matter. The lighter, nondissolved elements such as petroleum based segments will surface to the top of the caisson. The pollutant free water will then gravitate toward the pile lower end, thence pass freely into the surrounding body of water.
To assure that this pollutant free water is sufficiently clean to be passed into the surroundings, its quality is monitored on a continuous basis. This necessity often stems from governmental regulations that prohibit the discharge of any materials which contain petroleum products, into the surrounding water.
To assure the integrity of the discharge system, the herein disclosed sampling means is utilized for withdrawing specimens of the treated water prior to the latter being discharged from the pile. Further, the withdrawal is achieved by utilizing process gas as the driving medium for the withdrawal pump.
Toward facilitating the sampling operation, the instant apparatus permits a predetermined, set amount of water to be withdrawn from the disposal pile lower end. This withdrawal follows either a systematic sampling schedule, or a substantially continuous process. Thus, discrete water samples are withdrawn from a point preferably adjacent to the pile lower end where the water leaves the pile.
The sampling apparatus includes a gas powered prime mover which is communicated with a source of process gas at the water's surface. Operationally, the apparatus effectuates the ingestion of a set quantity of water to be sampled. The sample is then forced from the lower end of the pile, upwardly to a sampling station where it is withdrawn and submitted for analysis to determine its purity.
The sampling pump or prime mover is communicated with a source of compressed gas at, and controlled from the water's surface. Preferably this source comprises a supply of pressurized gas which has been extracted or separated as a result of the petroleum producing process.
It is therefore an object of the invention to provide a method to assure the integrity of discharged water at an offshore operating site. A further object is to provide means for continuously sampling a pool of water which is to be discharged into the surrounding water at an offshore site.